Methods of manufacturing electrical circuits

ABSTRACT

A METHOD OF MANUFACTURING CURRENT CONDUCTING CIRCUITRY ON A NON-CONDUCTIVE BASE IS PROVIDED WHICH INCLUDES THE STEPS OF APPLYING HEATED CUTTING EDGES OF A SELECTED CONFIGURATION TO A METAL FOIL SUPERIMPOSED OVER AN INSULATING BACKING STRIP TO SHEAR A CIRCUIT AND PRESS THE SHEARED EDGE AGAINST THE STRIP ADHERING THE EDGE TO THE STRIP, TRANSFERRING THE ASSEMBLY TO A PRESS, SUBJECTING THE ASSEMBLY TO A FIRST TEMPERATURE AND PRESSURE TO REMOVE GASES FROM BETWEEN THE FOIL AND STRIP, TO A SECOND HIGHER TEMPERATURE AND PRESSURE TO ADHERE THE FOIL TO THE BACKING STRIP, AND FINALLY TO A THIRD TEMPERATURE AND PRESSURE SUBSTANTIALLY EQUAL TO THE FIRST FOLLOWED BY COOLING UNDER SAID THIRD PRESSURE.

March 30, 1971 J. I. KOUGEL METHODS OF MANUFACTURING ELECTRICAL CIRCUITS Filed June 7, 1968 Fig.3.

Cufling 8 Attaching Fail To Substrate Pressing 8 Heating To SOOIbsJinT Br 250F.

Pressure 81 Temperature Increased To I450 lbs/inf e 320F.

Pressure B Temperature Decreased To 500 msmfe 280 F.

Coal To l00F. Under SOOIbs/in? Pressure INVENTOR Jack I. Kougel United States Patent 3,573,126 METHODS OF MANUFACTURING ELECTRICAL CIRCUITS Jack I. Kougel, Leesburg, Ind., assignor to GTI Corporation Filed June 7, 1968, Ser. No. 735,427 Int. Cl. B321) 31/26 US. Cl. 156251 3 Claims ABSTRACT OF THE DISCLOSURE A method of manufacturing current conducting circuitry on a non-conductive base is provided which includes the steps of applying heated cutting edges of a selected configuration to a metal foil superimposed over an insulating backing strip to shear a circuit and press the sheared edge against the strip adhering the edge to the strip, transferring the assembly to a press, subjecting the assembly to a first temperature and pressure to remove gases from between the foil and strip, to a second higher temperature and pressure to adhere the foil to the backing strip, and finally to a third temperature and pressure substantially equal to the first followed by cooling under said third pressure.

This invention relates to methods of manufacturing electrical circuits and particularly to die cut circuits in which an electrical circuit is cut by stamping from a sheet of metal or metal foil and applied to an insulative backing with an adhesive.

The use of heated metal embossing dies for cutting electrical circuits and applying them to an insulative backing member by means of the heated die is old. Such a practice is disclosed in Franklin Patent 2,622,054, Franklin Patent 2,647,852 and Franklin Patent 2,753,619. All of these patents use a heated cutting die which simultaneously cuts and attaches by adherence, a circuit design onto an insulating support which flows at the temperatures and pressures employed, from a sheet of metal coated on the side facing the support with thermo-responsive resin. These patents have met with limited success because of the problems of failure to achieve satisfactory adherence and the resultant partial stripping, breaking and the like of the metal from the support. This results in rejection of a large percentage of the product or unsatisfactory performance in subsequent operations.

I have invented a method of making die stamped circuits which substantially eliminates these problems of conventional die cut circuits.

Preferably I apply heated cutting edges of a selected configuration to a metal foil superimposed over an insulating backing strip to shear a circuit of said selected configuration and to press the sheared edge against said insulative backing strip, adhering said sheared edge to the backing strip, transferring said backing strip to a press, subjecting said strip and foil to a first temperature and pressure suflicient to cause all volatile material to flow from beneath the metal foil and permit the foil and backing to reach equilibrium and then to a second temperature and pressure sufficient to adhere the foil to the backing strip and finally to a third temperature and pressure substantially equal to said first temperature and pressure and thereafter cooling the adhered strip and foil under said third pressure to below 100 and removing the completed circuit from said press. Preferably a substantially non-flowing adhesive such as an epoxy resin is placed between the metal foil and backing strip before the cutting operation. This is preferably accomplished by 3,573,126 Patented Mar. 30, 1971 coating one side of the metal foil with adhesive. The assemblies of cut foil and backing strip are preferably assembled in books, separated by laminating pads, such as 50 lb. paper, and placed between platens which are free to move within the press to balance the load. Preferably I use a first temperature of 280 F. and a first pressure of 500 lbs./in. a second temperature of 320 F. and second pressure of 1450 lbs./in. and a third temperature and pressure identical to the first. Preferably I bump the press at the first temperature and pressure, that is to say I cyclically increase and decrease: the pressure slightly above and below the normal pressure several times. This practice, although not essential, helps to eliminate bubbles of gas between the metal foil and backing strip. Preferably I hold the first and third temperature and pressures for from 10 to 30 minutes but preferably about 20 minutes each and the second temperature and pressure for about 12 to 15 minutes.

In the foregoing general description I have set out certain objects, advantages and purposes of my invention. Other objects, purposes and advantages will be apparent from a consideration of the following description and the accompanying drawings in which:

FIG. 1 is a fragmentary section through a die and metal foil and backing strip according to my invention;

FIG. 2 is a side elevation of a press and load according to my invention;

FIG. 3 is a flow sheet of the process.

Referring to the drawings I have illustrated a heated embossing die 10 cutting foil 11 to a desired selected configuration and attaching the cut edges to a backing strip 12 by epoxy resin 13. Preferably the body of the foil 11 remains unattached so that gases are more readily expelled in the subsequent laminating pressure steps. The assembly 14 of cut foil 11 and backing strip 12 is stacked as books of assemblies separated by laminating pads 15 in the form of 50 lb. paper thickness) between platens 16 of a slab side press 17. The assemblies are heated in the press to approximately 280 F. and pressure at 500 lbs/in. is applied for about 20 minutes. The temperature is raised to 320 F. and the pressure to 1450 lbs/in. for about 12 minutes. The pressure is then lowered to 500 lbs/in. and the temperature to 280 F. This latter pressure is held until the assemblies cool (below approximately F.). As a backing strip, I have used Mylar, epoxy, phenolic resin impregnated papers, and similar resin materials. The adhesive may be any substantially non-flowing adhesive which will not bleed beyond about 0.010 inch at any point on the cut edge.

While I have illustrated and described certain preferred practices of my invention in the foregoing specification, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

I claim:

1. The method of manufacturing an assembly of current conducting circuitry on a non-conductive base comprising the steps of applying heated cutting edges of a selected configuration defining a current conducting circuit to a metal foil superimposed over an insulating backing strip with a thermo-responsive adhesive therebetween to shear a circuit of said selected configuration from said foil and to press the sheared edge defining said circuit against said insulating backing strip, adhering said sheared edge to the backing strip, transferring said assembly to a press, subjecting said assembly to a first temperature and pressure suflicient to cause substantially all gaseous material to flow from beneath the metal foil and then to a second temperature and pressure suflicient to firmly adhere the foil to the backing strip and finally to a third temperature and pressure substantially equal to the first temperature and pressure and thereafter cooling the assembly under said third pressure to below 100 F. and 2,969,300 removing the completed assembly from the press. 3,305,416 2. A method as claimed in claim 1 wherein the metal 3,331,726 foil is coated with a thermo-sensitive adhesive.

3. A method as claimed in claim 2 wherein the ad- 5 3,442,752

hesive is an epoxy resin.

References Cited UNITED STATES PATENTS 2,622,054 12/1952 Franklin 156-251 10 2,711,983 6/1955 Hoyt 174685 4 Franz l61--Print Circuit Kahan 156--286X McGinley et a1.

161Print Circuit Sandler et a1. 156-330X BENJAMIN A. BORCHELT, Primary Examiner D. BENT, Assistant Examiner US. Cl. X.R. 

